The present invention is in the field of genetically engineered organisms, particularly genetically modified exopolysaccharide producing strains of Zoogloea ramigera.
Polysaccharide biopolymers have found applications in many industries, including the food, cosmetic, chemical, biomedical, waste treatment and oil industries.
Flocculation is one important commercial use of biopolymers. Several types of floc-forming bacteria have been identified. The most efficient are the cellulose, or cellulose-like, producing bacteria such as certain species of Pseudomonas, Aerobacter, Agrobacterium, Azotobacter and Zoogloea. Flocculation of these bacteria appears to occur when cells become embedded in a network of exopolysaccharide fibrils. Other floc-forming bacteria produce capsular polysaccharides enclosing large packets of cells which lead to floc formation. An example of this phenomenon occurs with Zoogloea ramigera 115. In some cases these exocellular polysaccharides have metal ion binding properties.
Z. ramigera 115, designated ATCC 25935 by the American Type Culture Collection, Rockville, Md., is an exopolysaccharide matrix forming strain which, when grown in a nitrogen limiting medium, converts 60% (w/w) of the available glucose substrate into a water soluble capsular branched heteropolysaccharide composed of glucose and galactose in a molar ratio of 2:1 with approximately 3% to 5% pyruvate. The negatively charged carboxyl groups of the pyruvate are thought to be primarily responsible for the biopolymer's high affinity for heavy metal ions.
Due to the unique rheological and strong metal binding properties of the Zoogloea ramigera exocellular polysaccharide, it is desirable to isolate, characterize, express and modify the exopolysaccharide genes produced by Zoogloea ramigera strains. It is also desirable to provide the genes or complementary nucleotide sequences for production of exocellular polysaccharides produced by Zoogloea ramigera for use in synthesis of novel polysaccharides.
It is therefore an object of the present invention to provide nucleotide sequences which can be used to produce novel biopolymers, especially the Zoogloea ramigera exopolysaccharides.
It is still further object of the present invention to produce a system for production of biopolymers with enhanced rate and level of synthesis and greater ease in isolation of the biopolymers.